1. Field of the Invention
The present invention generally relates to an image input apparatus, an image input method, a recording medium, and an encryption processing program stored in a computer-readable medium. More particularly, the invention relates to a technique for protecting the copyright for image signals.
2. Description of the Related Art
In image input apparatuses, such as still cameras, video cameras, and scanners, all of which are of the analog type, analog image signals, such as motion pictures or still images, obtained by photographing subjects, are converted into recordable/reproducible signals, which are then output to an external source. Alternatively, such analog image signals are recorded on a recording medium by using a recording apparatus.
Generally, since the data in the above-described recording medium can be stored over a long period, it is suitable to observe or reuse the stored analog image information later. Accordingly, in response to the user's demand, a reproducing apparatus reads analog image information recorded on the recording medium and reconstitutes it to an image that can be viewed by humans. The image is then reproduced through an output apparatus, such as a printer or a display unit.
Because of recent progress in digital technology, analog-type image input apparatuses are gradually being replaced by digital-type image input apparatuses. In most cases, the digital-type image input apparatuses optically read a subject to be photographed and photoelectrically convert the image into an electric signal, which is then converted into a digital signal. Subsequently, the image input apparatuses perform predetermined image processing on the digital image. The resulting image information is then output to an external source as digital information of a predetermined data format.
The above predetermined data formats include coding systems for performing high-efficiency coding on image information, such as MH, MR, MMR, TIFF, JPEG, and MPEG.
A reproducing apparatus decodes the coded digital information by using decoding algorithms corresponding to the coding system used in the image input apparatus. The decoded information is then reproduced as the original image that can be viewed by humans through an output apparatus, such as a printer or a display unit.
The digital image information coded in the above-described predetermined data format will be simply referred to as “coded image information” hereinafter. It is, in general, very easy to incorporate the coded image information into an image processing apparatus, for example, a personal computer, and to edit the image information by using image information editing software.
According to the digital system, when the coded image information or the edited image information is copied, the image quality of the copied information is exactly the same as that of the original information. In contrast, the image quality of analog information is always degraded when copied. In view of maintaining image quality, the digital system is a significant improvement over the analog system.
In the analog system, however, the image quality of analog information is invariably degraded when copied. Accordingly, illegal copying does not present a serious practical problem.
On the other hand, in the digital system, it is possible to produce unlimited numbers of copies which are identical to the original. Accordingly, anyone is able to freely copy the original, i.e., consumers are able to copy a product, such as a movie, without paying a royalty for the copied movie to the copyright holder, which inevitably becomes a major problem for copyright holders.
Alternatively, if the original of the coded image information is recorded on a computer, the following may occur. A cracker may illegally access the computer and copy the image information, which may be then sold at a cost lower than the legitimate product, or it may be reedited and sold as another product.
As an effective countermeasure against the aforementioned copying of digital information, an encrypting technique may be used. To “encrypt” is to convert the original information into a coded form that is not understood by anyone other than authorized users.
Generally, an encryption operation is performed by information processing apparatuses, such as computers. More specifically, the original image produced by an image input apparatus is temporarily stored in an information processing apparatus and is then encrypted. A decryption key for decoding the encrypted image is safely stored within the information processing apparatus.
Thus, even if the encrypted image information recorded on the image processing apparatus is illegally copied, the illegal user is unable to read the content of the encrypted image information unless the decryption key is obtained. That is, by encrypting the original image in the information processing apparatus, the copyright of the image information can be safely protected.
As noted above, however, the original image produced in the image input apparatus is first output to the information processing apparatus and is then encrypted. If the image information is accessed during the period from which the image information is output from the image input apparatus to which it is encrypted in the information processing apparatus, such as a computer, there may be the danger of illegally copying the image information, thereby jeopardizing the security of the image information.
Additionally, a decryption key for decoding the encrypted image information, which is safely stored in the image information processing apparatus, may be illegally obtained by the users other than authorized users by using a new method of attack.